KUKA KRC4 and X11

  • Greetings people!


    I am working on an Agilus robot with KUKA KRC4 compact controller. I am using x11 as my safety interface (the robot was ordered with it). I am working on a scenario where there will be safety gates (light curtains, 2 pairs in total). I want the robot to completely stop when someone cuts any of the light curtains. The PLC I am using is a Sick safety PLC, and gives out +24V output. How do I connect my PLC outputs to the X11 interface? Is it like a direct connection using relays? If so can anyone shed some light on it? I went through other posts on this forum related to the same but they were of very little help. I went through the X11 manual as well, everything was clear other than this.


    Thanking you in advance. :)

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  • you would not want someone to build your car or house without knowing what they are doing and following safety standards - someone may get killed or hurt badly. same is with industrial machines and specially robots because they can move suddenly and at high speeds.


    robotic safety standards tend to call for safety circuits that are redundant and monitored (CAT 3 or 4, SIL2+)


    this means use of safety rated components because they are guaranteed to fail in predictable way. this is why safety components are rated and marked accordingly.

    redundant means more than one channel

    monitored means there are safety interlocks monitoring for failures. this also means preventing restart if failure was detected. there are different ways of monitoring, using diagnostic pulses or monitoring feedback loops.




    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

  • panic mode Thank you for replying. I understand and I am not going to integrate anything before having a proper knowledge about it. Thanks for the advice. What in your opinion would be the best way to do achieve the same i.e. safety using the outputs from the PLC to X11. Is safety relays the only option? This is just for research purposes and I am not implementing anything as of now.

  • well those are very vague questions. you are not communicating. please read pinned topic READ FIRST.

    if your hope is to get specific answer, you need to provide specific detail.


    you did not share where you are, what standards apply in your country, what is the EXACT model of the "PLC" etc. you need to read the datasheets and check what the safety outputs are. if they are relay contacts, you can wired them directly to X11. if they are OSSDs, there is a 99.9999% chance that they are with diagnostic pulses so interposing safety relays of some sort are needed. This is because KUKA safety inputs also use the pulse trains on Ta and Tb. In other words they are not solid DC voltage and if inputs get wired to a wrong "power" supply (Ta instead of Tb or the other way around) system will fault and you will need to rewire it.

    Diagnostic pulses in output signals from one device are not synchronized with diagnostic pulses on another device. And this is when you should add safety relays - even though they slow the signals down, because their contacts stay on during those very narrow diagnostic pulses. In other words pulses from safety PLC get filtered out and X11 inputs see pulses from their own controller.


    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

  • KRC4 supports three other types of safety interface that do not involve X11. those other interfaces however do require safety PLCs and communicaiton optoon (hardware/software).

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

  • Unless you have a Safety PLC, and that PLC has Safe I/O modules, you do not connect your PLC to X11. Period.


    Hardwired safety devices, like Light Screens and E-Stops, have dual-channel dry-contact "outputs", and X11 is built to work with them. Your LSs, for example, might be wired in series with each other, and into the Operator Safety contacts on X11, paying attention to the A and B channels as Panic described earlier. OpSafe disables the robot in AUT or EXT, but not in T1 or T2 (T2 can be very hazardous, so consider disabling or limiting it).


    E-Stops, OTOH, should only be wired to X11's E-Stop contacts.


    More complex safety circuits might involve wiring multiple devices into dedicated safety relays (not regular relays, but something like these), and then wiring the relay contacts to X11, the PLC, and whatever other parts of the machine need to be connected.


    Basic rules: if it's not Safety Rated, it doesn't connect to X11, ever. A single non-safe piece of hardware invalidates an entire safety chain. All safeties are dual-channel, with "fingerprinted" A and B channels.


    Frankly, you shouldn't set up robotic safety without understanding and implementing RIA 15.06, or have your setup performed or validated by someone who does.

  • panic mode  SkyeFire Thank you. That was quite informative. I'll keep all if these in mind.

    Another quick question, if the only safety configuration I am using is x11, then is there a way to reduce the robot speeds when lets say a light curtain is obstructed?

  • Safety light curtains are MEANT to reduce speed.... To zero. This is why they are wired to SAFETY inputs.

    But if you have a way to ensure safety per current standards, nothing is stopping you from using LC as a non-safety product. Get LC output to robot input (non-safety) and do as you please.

    Note laser scanner is product type with similar function to LC but usually has one or more warning fields.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

  • Without the correct Safe Operation option, there's no safety rated means of reducing the robot's speed based on an input. Plain regular X11 safety is very simplistic: the robot is safe to move (at any speed), or it's not safe to move at all.

  • Actually we have used Safety scanner as well but we had an extra pair of LC's lying around which is why we thought of using it as the outer most warning zone. If someone obstructs the outermost LC (on the 1st door), the velocity will be decreased and when someone enters the 2nd door (inside door 1 with another pair of LC), the robot would completely stop moving.

    The controller came with an X12 interface with Beckhoff modules already installed, which is what we were thinking to use. Is the system viable?

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